Heparin is currently used in parenteral administration for the prevention and treatment of deep venous thrombosis. Heparin and related derivatives are ineffective or are destroyed in the gastrointestinal tract by acid or enzymatic hydrolysis. In addition, the size and ionic charge of the molecules could prevent absorption.
Various adjuvants (for example, non-ionic surfactants) have been used to improve the oral absorption of heparin. Recently, modified amino acids have been used to facilitate the administration of various biological agents, in particular heparin (WO 98/34632, WO 01/51454, WO 97/36480).
These compounds are essentially derived from 4-amino-phenylbutyric acid:
and various amides such as:

In particular, the following derivatives

Primarily those derivatives relative to n=2 and n=5 (WO 97/36480) are claimed as agents that facilitate the oral absorption of biological products.